1. Field of the Invention
The present invention relates to a hybrid vehicle constructed so that running drive can be effected by transmitting engine output through a gear-change mechanism to the vehicle and running drive is also possible by means of a drive motor that is arranged in parallel with the engine, so that, in prescribed operating conditions, the engine may be temporarily stopped and running drive may be performed by driving the vehicle by means of the drive motor.
2. Description of the Related Art
Efforts are being made to put into practice hybrid vehicles wherein running can be performed using engine drive and electric motor drive in combination, with the object of improving engine fuel consumption, etc. Such a hybrid vehicle is disclosed for example in Laid-open Japanese Patent Application Number H.11-132321. This vehicle comprises an engine, a first motor generator connected to the engine crankshaft, a belt type infinitely variable gear-change mechanism connected to the engine output shaft through a torque converter, and a second motor generator connected to a power transmission system on the output side of this infinitely variable gear-change mechanism. This vehicle is arranged such that ordinary running is performed by converting the gear ratio of the engine driving force in the infinitely variable gear-change mechanism before transmitting it to the vehicle wheels; when the vehicle is temporarily stopped, the engine is also temporarily stopped; and when subsequently the vehicle is made to move off, the vehicle wheels are driven by a second motor generator. It should be noted that, when the vehicle is thus made to move off again, the engine is restarted by the first motor generator, and after the vehicle has moved off a changeover is effected to running using engine drive.
If the engine is thus stopped when the vehicle is temporarily stopped, hydraulic pump drive by the engine is also stopped, causing the hydraulic pressure of the infinitely variable gearchange mechanism to be lost. Accordingly, a second hydraulic pump is provided that is driven by an electric motor and when the engine is stopped a prescribed hydraulic pressure is generated by driving the second hydraulic pump by means of this electric motor so as to prepare for the next move-off in a condition with the gear ratio set to the maximum (LOW) to enable motive force transmission, by supplying this prescribed hydraulic pressure to the output pulley cylinder chamber of the infinitely variable gear-change mechanism. In this way, in a hybrid vehicle as described above, an improvement is sought to be achieved with respect to fuel costs by stopping the engine when the vehicle is temporarily stopped, and an improvement with respect to fuel costs is sought to be achieved by driving the vehicle wheels using the second motor generator when moving off.
Consideration has also been given, with the object of further improving the fuel consumption, to stopping the engine and performing running using the electric motor drive also when the vehicle is running at comparatively high speed. If, in this case, the conventional hybrid vehicle control described above is employed without modification, the following problems arise.
Conventionally, when the engine was stopped in a condition where the vehicle was temporarily stopped, it was arranged for the clutch, which is provided in the power transmission system, to be prepared for the next move-off by being in an engaged condition, by hydraulic fluid pressure supplied from the second hydraulic fluid pump during the engine stoppage. However, if the clutch is put in engaged condition when the engine is stopped during running, the problem arises that the gear-change mechanism and the torque converter are rotated by the driving force from the vehicle wheels, generating entrainment torque, necessitating additional driving torque from the electric motor, thereby lowering drive efficiency. This is the reason why the clutch is disengaged when running is performed by means of the electric motor drive with the engine stopped.
However, when the arrangement is made such that the clutch is disengaged while running is performed using the electric motor drive, that is, the clutch is engaged and disengaged during the running by the engine drive and during the running by the electric motor drive, respectively, problems will arise if the controllability of engaging and disengaging the clutch is lowered that the switching over can not be done at a required timing, or a shock is created during the switching over operation. For example, in a case when the clutch engagement/disengagement control is performed by the use of hydraulic pressure, such problems will arise if a control valve for control of hydraulic engagement/disengagement of the clutch deteriorates or causes malfunction.
Further, there will also be a problem that the clutch is left in its disengaged state and becomes unable to be engaged due to the malfunction of the control valve, and in such a case the running performance of the vehicle is deteriorated. For example, in a case of a clutch that is engaged/disengaged by hydraulic pressure, such problem will arise if the spool of a control valve that control supply of working hydraulic pressure to the clutch is fixed at the position to block the supply of working hydraulic pressure due to its sticking. If the clutch is left in the disengaged state in this way, the output of the activated engine can not be transferred to the vehicle wheels, whereby the vehicle will be forced to travel only with the electric motor drive, without the engine drive and can not obtain sufficient driving force.
An object of the present invention is to provide a hybrid vehicle control device of a construction wherein means for engagement/disengagement such as a clutch are engaged/disengaged during running using an electrically driven motor drive and running using engine drive, such that engagement of the means for engagement/disengagement can be effected even when abnormality (electrical malfunction, i.e., failure of the gear-change mechanism and/or malfunction of the control valve etc) of the means for controlling the engagement/disengagement action of the means for engagement/disengagement occurs, without being affected by such abnormality.
According to the present invention, there is provided a hybrid vehicle comprising: an engine capable of temporary stoppage control in a prescribed operating condition, a gear-change mechanism (for example infinitely variable gear-change mechanism 20) connected to the output shaft of this engine and whereby its output rotation is changed in gear ratio; a driving force transmission system (for example, idler shaft 31, final drive gear 32, final driven gear 33, differential mechanism 34, and axle shafts 35) that transmits the output of this gear-change mechanism to the driven wheels; an electrically driven motor (for example, second motor generator 50) capable of driving said driven wheels and connected to this driving force transmission system, and means for engagement/disengagement (for example forwards/reverse changeover mechanism 10) arranged in a path from the output shaft of said engine to said driving force transmission system and that perform engagement/disengagement control, arranged such that running drive can be performed by transmission of the output of the engine to the driven wheels through the gear-change mechanism and power transmission system by engagement of the means for engagement/disengagement and running drive can be performed by transmission of driving force of the electrically driven motor to the driven wheels in a condition with the means for engagement/disengagement released. Furthermore, this control device comprises auxiliary means for engagement control that, when abnormality of the gearchange mechanism is detected, are capable of engaging the means for engagement/disengagement without being affected by this abnormality, and is such that, when, in a condition with the means for engagement/disengagement released, running drive is performed by transmitting the driving force of the electrically driven motor to the driven wheels, if abnormality is detected, the means for engagement/disengagement are engaged by the auxiliary means for engagement control and running is effected by driving the engine instead of the electric motor.
If a hybrid vehicle control device constructed in this way is employed, even if an abnormality is detected when running drive is performed by transmitting the driving force of the electrically driven motor to the driven wheels in a condition with the means for engagement/disengagement released, for example, control can be effected such as to engage/disengage the means for engagement/disengagement by using the auxiliary means for engagement control. Because the auxiliary means for engagement control constitute means capable of effecting engagement of the means for engagement/disengagement unaffected by abnormality, excellent and reliable engagement control of the means for engagement/disengagement can be performed by the auxiliary means for engagement control even if abnormality is detected during running, so, even when abnormality occurs, the means for engagement/disengagement can be engaged/disengaged with good timing and in a smooth manner (without shock). Also, if an abnormality is detected in a condition in which running drive is being performed by the electrically driven motor in a condition with the means for engagement/disengagement released, a shift to running drive using the engine can be reliably achieved by engaging the means for engagement/disengagement by the auxiliary means for engagement control, stopping this drive by stopping supply of driving power to the electric motor, and driving the engine.
The means for engagement/disengagement may comprise a hydraulic pressure type means for engagement/disengagement that perform engagement/disengagement control using hydraulic pressure force, and the auxiliary means for engagement control may comprise an engagement/disengagement control valve (for example, forwards/reverse clutch control valve 73) that controls hydraulic pressure supply and cut-off for engagement/disengagement control of the hydraulic means for engagement/disengagement, and auxiliary means for supplying hydraulic pressure (for example shift inhibitor valve 77, shift control valve 66, auxiliary changeover valve 85, and auxiliary changeover solenoid valve 83) capable of supplying hydraulic pressure for engagement/disengagement control to the means for engagement/disengagement when supply of hydraulic pressure to the means for engagement/disengagement is cut off by this engagement/disengagement control valve. In this case, the arrangement is such that, if abnormality is detected in a condition with supply of hydraulic pressure to the means for engagement/disengagement cut off by the engagement/disengagement control valve, supply of engagement/disengagement control hydraulic pressure to the means for engagement/disengagement can be performed by the auxiliary means for supplying hydraulic pressure.
Using a control device of such a construction, even if, for example, an abnormality is detected in a condition with the means for an engagement/disengagement being released (disengaged) by cutting off supply of hydraulic pressure to the means for engagement/disengagement by the engagement/disengagement control valve, or in a condition with the means for engagement/disengagement that are supplied with hydraulic pressure being engaged, control whereby the means for engagement/disengagement are engaged/disengaged can be performed in excellent fashion by supplying engagement/disengagement control hydraulic pressure to the means for engagement/disengagement by the auxiliary means for supplying hydraulic pressure. Because the auxiliary means for supply of hydraulic pressure constitute means capable of supplying engagement control hydraulic pressure to the means for engagement/disengagement is unaffected by an abnormality, excellent and reliable engagement control of the means for engagement/disengagement can be performed by the auxiliary means for supplying hydraulic pressure even if abnormality is detected during running, so, even when abnormality occurs, the means for engagement/disengagement can be engaged/disengaged with good timing and in a smooth manner (without shock). Consequently, even if, when running drive is being performed using the electrically driven motor in a condition with, for example, the engine temporarily stopped and the means for engagement/disengagement released by cutting off supply of the engagement/disengagement control hydraulic pressure to the means for engagement/disengagement, an abnormality such as malfunction of the engagement/disengagement control valve occurs making it impossible to re-engage the means for engagement/disengagement, re-engagement of the means for engagement/disengagement can be achieved by supplying engagement/disengagement control hydraulic pressure to the means for engagement/disengagement by the auxiliary means for supplying hydraulic pressure, upon detection of this abnormality. As a result, the situation of engine drive becoming impossible due to malfunction of the engagement/disengagement control valve is reliably prevented.
The auxiliary means for supplying hydraulic pressure may comprise: a first auxiliary changeover valve (for example, shift inhibitor valve 77) capable of changeover movement between a normal position in which normal control hydraulic pressure is supplied to the means for gear-change control of said gear-change mechanism and a fail position in which fail control pressure is supplied, and first auxiliary means for operation control (for example, shift control valve 66) that performs position changeover operation control of this first auxiliary changeover valve. In this case, the first auxiliary changeover valve is provided with a port that communicates with the means for engagement/disengagement through the engagement/disengagement control valve when the engagement/disengagement control valve is in a condition cutting off supply of hydraulic pressure to the means for engagement/disengagement, where this port communicates with the drain when the first auxiliary changeover valve is in the normal position and communicating with an engagement/disengagement control hydraulic pressure supply source when it is in the fail position, and is arranged such that, under normal conditions, the first auxiliary means for operation control positions the first auxiliary changeover valve in the normal position and, if abnormality is detected, the first auxiliary means for operation control positions the first auxiliary changeover valve in the fail position.
If a control device constructed in this way is employed, even if, for example, when running drive is being performed using the electrically driven motor in a condition with the engine temporarily stopped and the means for engagement/disengagement released by cutting off supply of the engagement/disengagement control hydraulic pressure to the means for engagement/disengagement, an abnormality such as malfunction of the engagement/disengagement control valve occurs making it impossible to re-engage the means for engagement/disengagement, control to engage the means for engagement/disengagement can be achieved by supplying engagement/disengagement control hydraulic pressure to the means for engagement/disengagement through the aforesaid port from the engagement/disengagement control hydraulic pressure supply source by the first auxiliary means for operation control positioning that first auxiliary changeover valve in the fail position on detection of this abnormality. Consequently, even when an abnormality occurs, control can be exercised such that the means for engagement/disengagement are engaged/disengaged with suitable timing and in a smooth manner, so the situation of engine drive becoming impossible can be reliably prevented.
Also, the auxiliary means for supplying hydraulic pressure may comprise: a second auxiliary changeover valve (for example auxiliary changeover valve 85) comprising a port that communicates with the means for engagement/disengagement through the engagement/disengagement control valve when the engagement/disengagement control valve is in a condition cutting off supply of hydraulic pressure to the means for engagement/disengagement, and second auxiliary means for operation control (for example, auxiliary changeover solenoid valve 83) that cause changeover movement between a drain position in which the port communicates with the drain and a supply position in which said port communicates with an engagement/disengagement control hydraulic pressure supply source, by performing operation control of the second auxiliary changeover valve. In this case, under normal conditions, the second auxiliary means for operation control positions the second auxiliary changeover valve in the drain position and, if abnormality is detected, the second auxiliary means for operation control positions the second auxiliary changeover valve in the supply position.
Thus, if a control device of such construction is employed, if, when running drive is being performed using the electrically driven motor in a condition where the means for engagement/disengagement is released, an abnormality such as malfunction of the engagement/disengagement control valve occurs making it impossible to re-engage the means for engagement/disengagement, engagement of the means for engagement/disengagement can be achieved by supplying engagement/disengagement control hydraulic pressure through the aforesaid port from the engagement/disengagement control hydraulic pressure supply source to the means for engagement/disengagement by the second auxiliary means for operating control positioning the second auxiliary changeover valve in the supply position. As a result, the situation of engine drive becoming impossible due to malfunction of the means for engagement/disengagement can be reliably prevented with this control device.
Further applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.